1. Field of the Invention
This invention relates to an ink jet recording apparatus in which ink is caused to fly by the utilization of pressure, preferably heat energy, to thereby effect recording on a recording medium.
2. Related Background Art
An ink jet recording apparatus is provided with a construction in which ink is supplied to a recording head and energy generating means is driven on the basis of recording information, whereby the ink is discharged from ink discharge ports to thereby form flying ink droplets and the ink droplets are caused to adhere to a recording medium disposed in opposed relationship with the recording head to thereby accomplish recording.
In the recording apparatus of this kind, as shown in FIG. 6 of the accompanying drawings, ink 12 or foreign substances including dust may sometimes adhere to the discharge port forming surface of the recording head including the discharge port portion. In order to remove such ink and foreign substances, there is often provided a cleaning member such as a cleaning blade for cleaning the discharge port forming surface.
Now, as the cleaning member of the prior-art ink jet recording apparatus, there has been proposed one which, as shown, for example, in Japanese Laid-Open Patent Application No. 61-230947, is designed to be put in and out to remove ink adhering to the discharge port forming surface of the recording head after the use of a recovery pump, or one, which, as shown in Japanese Laid-Open Utility Model Application No. 58-128034, is designed to contact with a recording head returned to a home position set in a non-recording area, always with a predetermined amount of contact, a predetermined thickness, predetermined dimensions and a predetermined number of cleaning blades.
Also, as shown in Japanese Laid-Open Patent Application No. 58-94472, there has been proposed one in which a blade is disposed within the deceleration section of a carriage when a recording head carried on the carriage is returned to the non-recording area side, and cleaning is effected in the decelerated condition of the carriage.
Further, as shown in Japanese Laid-Open Patent Application No. 59-14964, there has been proposed one in which a cleaning blade provided on an endless belt disposed in opposed relationship with the discharge port forming surface of a recording head is rotated from up to down to thereby effect cleaning.
In these examples of the prior art, however, the possible cleaning condition for the discharge port forming surface of the recording head is always made simply constant irrespective of the recording condition or irrespective of the difference in recording mode and therefore, there have been cases where the cleaning condition is good in the early stage of cleaning, but when the recording condition or the recording mode changes, sufficient cleaning cannot be accomplished depending on the recording mode, that is, unsatisfactory cleaning begins to take place intermittently and finally, after a long-time use, unsatisfactory cleaning takes place in every recording mode.
Accordingly, the stable obtainment of a long-period cleaning effect has heretofore not been achieved sufficiently.
In view of the above-noted problem, we have made one study after another and have made the following matter clear.
Usually in cleaning, one kind of cleaning condition is set. In this case, the set condition for cleaning is suited for particular one of a plurality of recording modes and therefore, a good result has been obtained in the process wherein this particular recording mode is continued.
In the other recording mode, however, unsatisfactory cleaning has gradually begun to take place and when the other recording mode and said particular mode have been repetitively carried out, unsatisfactory cleaning has gradually begun to take place even in the particular mode wherein good cleaning was seen at the beginning, and the result has been a case where in the two modes, there takes place unsatisfactory cleaning as shown in FIG. 4 of the accompanying drawings.
Further examinations on the basis of the above findings revealing the following:
i) When the recording mode is changed, for example, the scanning speed of a carriage carrying a recording head thereon is changed as in the so-called NLQ (near letter quality) recording wherein recording is effected at a low speed to thereby obtain records of high quality and the so-called draft recording wherein recording is effected at a high speed, the state of contact of the cleaning member with the discharge port forming surface of the recording head differs and gives rise to various influences. That is, the cleaning member mounted on the apparatus side is installed in a predetermined condition and therefore, when the speed of movement of the carriage is high as in the draft recording, the shock during the contact of the cleaning member with the discharge port forming surface is strong and the influence of the contact may result in the retraction of the meniscus position formed in the discharge ports, which in turn may result in unsatisfactory discharge attributable to the entry of bubbles and the retraction of the meniscus.
Or when the speed of movement of the carriage is low as during the NLQ recording, the state of contact of the cleaning member with the discharge port forming surface becomes weak and ink or foreign substances adhering to the discharge port forming surface cannot be sufficiently removed and a pool of ink may be created by incomplete wiping, and this may cause unsatisfactory discharge. That is, where a predetermined cleaning condition is set, the apparent state of contact of the cleaning member with the discharge port forming surface (the cleaning condition) differs by the recording speed condition being changed.
That is, it is preferable in effecting good cleaning of the discharge port forming surface to adopt a construction in which as the speed of the carriage becomes higher as in the aforedescribed draft recording, the amount of contact of the wiper with the discharge port forming surface is made smaller and as the speed of the carriage becomes lower as in the aforedescribed NLQ recording, the amount of contact of the wiper with the discharge port forming surface is made greater to thereby make the apparent state of contact constant.
ii) The amount of ink adhering to the discharge port forming surface is varied by a variation in the recording density, i.e., a variation in the number of discharge ports which discharge the recording liquid per unit time, whereby the state of contact of the cleaning member with the discharge port forming surface of the recording head becomes different and this gives rise to various influences.
That is, the cleaning member mounted on the apparatus side is installed in a predetermined condition as previously described and therefore, for example, when high density recording is effected, the amount of ink adhering to the discharge port forming surface becomes greater. When the cleaning of the discharge port forming surface to which a great amount of ink droplet has adhered is effected by the cleaning member, the contact of the cleaning member with the discharge port forming surface cannot be sufficiently be accomplished due to the surface tension of the adhering ink and the amount of adhering ink, and this may sometimes result in the deterioration of the state of contact, and removal of the ink and foreign substances cannot be accomplished sufficiently and a pool of ink is created by incomplete wiping, and this may cause unsatisfactory discharge.
Or when low density recording is effected, not so much ink adheres to the discharge port forming surface and therefore, the shock during the contact of the cleaning member with the discharge port forming surface is strong and this may result in the retraction of the meniscus, which may cause unsatisfactory discharge attributable to the entry of bubbles and the retraction of the meniscus. That is, when a predetermined cleaning condition is set, the apparent state of contact of the cleaning member with the discharge port forming surface (the cleaning condition) becomes different by the recording density condition being changed.
That is, it is preferable in effecting good cleaning of the discharge opening forming surface to adopt a construction in which as the recording density becomes lower, the amount of contact of the cleaning blade with the discharge port forming surface is made smaller and as the recording density becomes higher, the amount of contact of the cleaning blade with the discharge port forming surface is made greater to thereby make the apparent state of contact constant.